Allow np.array in DefPermutationGate

[notmgsk]

Description

Closes #1223. DefPermutationGate supported a permutation of type list or np.ndarray of shape (N, 1). Alas, something like np.array([0, 1]) wasn't supported because its shape looks like (N,). C'est la vie. Cast to np.ndarray early.

Checklist

• The above description motivates these changes.
• There is a unit test that covers these changes.
• All new and existing tests pass locally and on Travis CI.
• Parameters and return values have type hints with PEP 484 syntax.
• Functions and classes have useful Sphinx-style docstrings.
• All code follows Black style and obeys flake8 conventions.
• (New Feature) The docs have been updated accordingly.
• (Bugfix) The associated issue is referenced above using auto-close keywords.
• The changelog is updated, including author and PR number (@username, gh-xxx).